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Hierarchical clustering analysis for the distribution of origanum-oil components in dense CO₂
Ugur Akman,Nesrin Okay,Oner Hortaçsu 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.2
Hierarchical Clustering (HC) technique is demonstratively applied to analyze the distribution and classification of essential-oil components in oil and dense (subcritical/supercritical) CO₂phases. For this purpose, relative-equilibrium- distribution data obtained for the 24 characteristic components of origanum-oil (Origanum Munituflorum) at 35, 45, 55 oC and 20-110 atm pressure range are used. With 24 components and 25 different pressure levels at three different temperatures, the total number of data points amounts to 600, which is large compared to other similar works, making the task of drawing of conclusions by visual inspection quite tedious. As demonstrated in this work, the use of HC technique facilitates the classification of the distribution of essential-oil components. HC-based classification analysis helps to reveal that the distributions of monoterpenes are the most sensitive to changes in temperature and pressure, and they are more soluble in CO₂ especially in the supercritical region. At 35 oC, at higher pressures, due to high solvent density/power, almost all components show similar distributions in the CO₂ and oil phases, indicating the loss of fractionation potential. Deterpenation by CO₂ is more favorable at higher temperatures. Cophnetic correlation shows the significance level of data clustering. HC analysis proved to be a useful tool in classification of the components and in determination of component clusters in the dense-gas and liquid phases.
Hugo Horta 서울대학교 교육연구소 2013 Asia Pacific Education Review Vol.14 No.4
This study analyzes the impact of intra-sectoral mobility of academics on research productivity and R&D information exchange dynamics in Japan. The analysis shows intra-sectoral mobility impacting positively both research productivity and information exchange dynamics, but that this effect—except for information exchange with peers based abroad—has a threshold. This result highlights the importance of academic job mobility but also alerts for cases of “overloads of mobility,” leading us to argue for some degree of stability in academic careers, supported by policies fostering temporary international mobility spells. We also find that the role of foreign academics in the Japanese higher education is one of national and international gatekeepers being this role shaped by where the doctorate was obtained (Japan vs abroad). Japanese academics that have performed the doctorate abroad are also key international gatekeepers.
Hugo Horta 서울대학교 교육연구소 2018 Asia Pacific Education Review Vol.19 No.2
This study explores the association between PhD students’ self-perception of skills and their career plans, which are analytically transformed into three non-academic sectors in relation to the academic sector (which serves as the baseline). Drawing on a representative sample of PhD students at a globally oriented research university in Asia (the University of Hong Kong), and using factor analysis, cluster analysis, and regressions, the study finds that self-perception of skills and career plans of PhD students are associated. These findings show that students with a strong perception of managerial skills are more inclined to consider career paths outside academia upon graduation. The study also finds that student perceptions of having strong managerial skills are more conducive for considering a career outside academia than having a strong aggregate self-perception in a broad set of skills. Further differences in the association between self-perception of skills and career plans are found for STEM and non-STEM PhD students. The initial motivation to earn a PhD remains strong throughout doctoral study programs and strongly predicts goal-associated career choices upon graduation. Finally, this study discusses the implications of these findings and makes policy recommendations.
Hugo Duarte Alves Horta,Machi Sato,Akiyoshi Yonezawa 서울대학교 교육연구소 2011 Asia Pacific Education Review Vol.12 No.1
This study analyses why and how academic inbreeding as a recruitment practice continues to prevail in Japan, a country with a mature higher education system, where high rates of academic inbreeding endure in most of the research-oriented universities in spite of several higher education reforms. Based on a qualitative analysis, we disclose three characteristics that lead academics to become inbred at Japanese universities. One characteristic-the adoption of "open recruitment processes" in detriment of "closed recruitment processes"—changed over time, limiting academic inbreeding practices, but two other characteristics remained unchanged over time: the "one university learning experience" and the "concentration of doctoral supervisors at the same university". These latter characteristics represent difficult challenges to be tackled as they are also traditional characteristics of the Japanese higher education system. The research also shows that academic inbreeding practices are a means to assure organizational stability and institutional identity, features perceived as important by Japanese universities. A central challenge for the Japanese universities is then to guarantee these features without needing to rely on academic inbreeding practices to obtain them. However, devising policies to meet this challenge calls for institutional will to change, proactive strategies and time.
Carriao, Paulo Cesar,Lisboa, Narciso Horta,Miyagaki, Olimpio Hiroshi Korean Mathematical Society 2013 대한수학회보 Vol.50 No.3
We deal with the existence of positive radial solutions concentrating on spheres for the following class of elliptic system $$\large(S) \hfill{400} \{\array{-{\varepsilon}^2{\Delta}u+V_1(x)u=K(x)Q_u(u,v)\;in\;\mathbb{R}^N,\\-{\varepsilon}^2{\Delta}v+V_2(x)v=K(x)Q_v(u,v)\;in\;\mathbb{R}^N,\\u,v{\in}W^{1,2}(\mathbb{R}^N),\;u,v>0\;in\;\mathbb{R}^N,}$$ where ${\varepsilon}$ is a small positive parameter; $V_1$, $V_2{\in}C^0(\mathbb{R}^N,[0,{\infty}))$ and $K{\in}C^0(\mathbb{R}^N,[0,{\infty}))$ are radially symmetric potentials; Q is a $(p+1)$-homogeneous function and p is subcritical, that is, 1 < $p$ < $2^*-1$, where $2^*=2N/(N-2)$ is the critical Sobolev exponent for $N{\geq}3$.